spare batteries for lights and GPS (don't forget a charger if you use accumulators),

12 V GSM charger (optional),

distributor (to connect more than one charger in the marine),

white buoy for safer anchoring,

Elvis,

camera,

make a whole week menu for food (usually strong breakfast and late dinner). Think about small snack around noon (chocolate and cookies are the best). Expect lack of dishes and space for preparing food. Refrigerator storage is limited, but there is plenty of room elsewhere.